Fuel injection

ABSTRACT

A SOLENOID OPERATED FUEL INJECTOR DISCHARGES INTO AN INTERNAL COMBUSTION ENGINE INDUCTION PASSAGE ADJACENT THE COMBUSTION CHAMBER INTAKE PORT. FUEL IS SUPPLIED TO THE INJECTOR THROUGH A TUBULAR FUEL RAIL WHICH IS RECEIVED BY AND CLAMPED IN A RECESS AT THE TOP OF THE INJECTOR. A THERMISTOR SENSES INJECTOR TIP TEMPERATURE AND CONTROLS THE DURATION OF ENERGIZATION OF THE SOLENOID TO COMPENSATE FOR A REDUCTION IN FUEL DELIVERY AT HIGH TEMPERATURES.

J. W. MOULDS FUEL INJECTION Sept. 20, 1971 Filed May 22, 1970 ZZZ United States Patent ice 3,605,703 FUEL INJECTION John W. Moulds, Penfield, N.Y., assignor to General Motors Corporation, Detroit, Mich. Filed May 22, 1970, Ser. No. 39,627 Int. Cl. F02m 51/00 US. Cl. 123-321 1 Claim ABSTRACT OF THE DISCLOSURE A solenoid operated fuel injector discharges into an internal combustion engine induction passage adjacent the combustion chamber intake port. Fuel is supplied to the injector through a tubular fuel rail which is received by and clamped in a recess at the top of the injector. A thermistor senses injector tip temperature and controls the duration of energization of the solenoid to compensate for a reduction in fuel delivery at high temperatures.

This invention relates to an internal combustion engine fuel system wherein fuel is metered by controlling the time duration that an injection valve is held open by a solenoid. It has been discovered that, with such a system, engine operation may be erratic due to improper fuel metering at the high temperatures which occur during a hot idle or after a hot soak. This has been attributed to the formation of vapor bubbles which reduce the fuel density and thus the total amount of fuel delivered. Initial attempts to correct this involved varying fuel metering in accordance with the temperature of the fuel in the fuel line leading to the injector. I have found, however, that a greater improvement in operation is achieved by compensating fuel metering in accordance with the temperature of the injector near its tip.

The details as well as other objects and advantages of this invention are set forth below and shown in the drawing which illustrates a solenoid operated fuel injector assembled to an engine and shows the injector-fuel rail interconnection and the thermistor disposed in heat exchange contact with the injector tip; a schematic electrical control circuit for energizing the injector solenoid is also shown.

Referring to the drawing, a fuel injector discharges into an internal combustion engine induction passage 12 below the throttle 14 and against the back of the intake valve 16 for a combustion chamber 18.

Injector 10 has a body 20 which is rolled over at one end 22 about a nozzle or tip 24. An 0 ring 26 is secured between body 20 and tip 24 to prevent leakage therebetween. A plunger 28 is guided at 30 in a passage 32 through tip 24 and has a head 34 received in a passage 36 through body 20. A central bore 38 through plunger 28 has lateral openings 40 and provides a fuel passage from body passage 36 to tip passage 32. Plunger 28 has a valve member 42 which seats in a discharge orifice 44 in tip 24. As plunger head 34 and plunger 28 are lifted, fuel is discharged through orifice 44 into induction passage 12.

A solenoid 46 wound on a plastic spool 48 is received in injector body 20. An 0 ring 50 provides a seal against fuel leakage between spool 48 and injector body 20. The end 52 of injector body 20 is swaged over and retains an inlet fitting 54. An 0 ring 55 provides a seal against fuel leakage between solenoid spool 48 and inlet fitting 54. Inlet fitting 54 carries a threaded member 56 which may be adjusted to vary the pre-load on a spring 58 biasing plunger head 34 and plunger 28 ot seat valve 42 in orifice 44.

When solenoid 46 is energized, the force across an air gip 60 between plunger head 34 and the extension 61 of 3,605,703 Patented Sept. 20, 1971 inlet fitting 54 raises plunger head 34 and plunger 28 to permit fuel flow through orifice 44. A flange 62 on plunger 28 engages a spacer disc 64 to limit upward movement of plunger 28.

Inlet fitting 54 has a longitudinal passage 66 which connects with passage 36 to deliver fuel to nozzle or tip 24. A pair of transverse openings 68 connect with longitudinal passage 66, and outwardly concave recesses 70 surround openings 68. A pair of tubular fuel rail members 72 are received in recesses 70 and have end surfaces 74 which abut the bases 76 of recesses 70. A pair of 0' rings 78 provide seals between the peripheral walls 80 of recesses 70 and the circumferential surfaces 82 of fuel rail members 72 to prevent fuel leakage therebetween.

Radially enlarged beads 84 on fuel rail members 72 are engaged by a retainer clamp 86. Legs 88 of clamp 86 overlie recesses 70 and have fingers 90 which embrace fuel rail members 72 and abut beads 84 to prevent withdrawal of fuel rail members 72 from recesses 70. A leg 92 of clamp 86 overlies the end 94 of inlet member 54 and has an aperture 96. The shank 97 of retainer screw 98 extends through aperture 96 and is secured to inlet member 54 while the head 99 of screw 98 overlies leg 92. An 0 ring 100 is secured between inlet member 54 and retainer screw 98 to prevent fuel leakage therebetween.

It will be appreciated that assembly of a fuel rail member 72 to injector 10 is a relatively easy task, requiring only insertion of fuel rail member 72 into recess 70, fitting of retainer clamp 16 over member 72 and inlet fitting 54, and securing of retainer screw 98.

In operation, a fuel pump 102 supplies fuel from a tank 104 through fuel rail 72 to longitudinal passage 66 within injector inlet fitting 54. When injector plunger 28 is lifted by solenoid 46, fuel passes through the wire cloth filter 106 and the longitudinal injector passages to the engine. Excess fuel is discharged through a pressure regulator 108 back to fuel tank 104.

Injector 10 has a grommet 110 surrounding tip 24 and sealing tip 24 in the engine. A clamp ring 112 is received in a recess 114 of injector body 20. A washer 116 and a clamp 118, secured by screws 120, retain injector 10 in place. One of the screws 120 also retains a spring clamp 122 which holds a thermistor 124 against injector body 20 and in heat exchange contact with injector nozzle or tip 24. Thermistor 124 controls fuel metering as explained below.

As mentioned above, fuel is metered by controlling the duration of time solenoid 46 is energized to operate injector 10. To energize solenoid 46, a signal generator 126, which nominally may be considered as a normally open switch, provides a negative voltage pulse during each cycle of the engine. This pulse is differentiated by a capacitor 128 into a negative going voltage spike Which is delivered to the base 130 of a transistor 132. Transistor 132 thus ceases to conduct, and the voltage at its collector 134 increases to render a transistor 136 conductive. The voltage at the collector 138 of transistor 136 then drops and an amplifying transistor 140 stops conducting. The voltage at the collector 142 of transistor 140 is thereby increased, and solenoid 46 is energized to operate injector 10.

As transistor 136 starts conducting, current passes through a primary winding 144. Primary winding 144 is coupled, through a core 146 positioned by a manifold absolute pressure responsive transducer 148, with a secondary winding 150. As current changes in primary winding 144, a voltage is induced in secondary winding 150 which biases base 130 of transistor 132 in a negative direction and holds transistor 132 in a non-conductive state. Over a period of time the rate of change of current in primary winding 144 drops, and the voltage induced in secondary winding 150 reduces sufiiciently to render transistor 132 conductive and terminate energization of solenoid 46.

In order to control the duration of time solenoid 46 is energized, thermistor 124 controls the impedance in the circuit of primary winding 144. Thus thermistor 124, together with resistors 152, 154, and 156, controls the current supplied to primary winding 144. The resistance of thermistor 124 decreases as the temperature of injector tip 24 increases; this increases the current flow through primary winding 144 to lengthen the time that solenoid 46 is energized.

In a fuel injection system where pressure regulator 108 maintains a pressure of 40 psi. in fuel rail 72, it is suggested that thermistor 124 be selected so that its resistance starts to decrease at 140 F. and so that the duration of energization of solenoid 46 increases linearly to a duration at 200 F. about 24% greater than the duration of 140 F. This will permit delivery of the proper amount of fuel through injector 10 despite a decrease in fuel density due to formation of vapor bubbles.

From the foregoing it will be appreciated that erratic engine operation during hot idle or after a hot soak may not be explained entirely by the fact the fuel temperature has increased; for instance, We have noted that supplying cool fuel to the injectors does not immediately result in improved operation. With this invention, however, satis factory operation is achieved throughout the high temperature range.

I claim:

1. A fuel injection system for an internal combustion engine comprising a fuel injection nozzle having a housing defining a passage for discharging fuel to said engine, a valve in said passage controlling the discharge of fuel to said engine, means for opening said valve for a controlled period of time during each operating cycle of the engine to thereby permit discharge of a controlled quantity of fuel to said engine, and means disposed in heat exchange contact with said housing and responsive to the temperature thereof for adjusting said controlled period of time whereby said controlled period of time may be lengthened to increase the quantity of fuel discharged when the temperature of said housing increases above a predetermined level, thus compensating for a reduction in fuel density due to formation of vapor bubbles in said nozzle above said temperature level.

References Cited UNITED STATES PATENTS 3,203,410 8/1965 Scholl l23'll9 LAURENCE M. GOODRIDGE, Primary Examiner US. Cl. X.R.

12332EA, 139E, 179A 

